Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

SYCR: Symposium Chemical Reactions on Nanomaterials: Progress from in-situ Experimental Studies and Theoretical Investigations

SYCR 1: Chemical Reactions on Nanomaterials

SYCR 1.5: Hauptvortrag

Donnerstag, 26. März 2009, 16:30–17:00, BAR SCHÖ

Live STM and X-ray observations of catalytic processes — •Joost W.M. Frenken — Kamerlingh Onnes Laboratory, Leiden University, The Netherlands

Catalytic processes are followed in situ with two dedicated instruments: the ReactorSTM and the ReactorSXRD. Both instruments allow us to investigate the surface structure of a model catalyst with atomic precision under realistic reaction conditions, i.e. at high temperatures in a flow of a reactive gas mixture at pressures up to several atmospheres. The two techniques, Scanning Tunneling Microscopy and Surface X-Ray Diffraction, provide complementary information on the structure and the morphology of the catalyst surface. Simultaneously with this, both instruments use mass spectrometry to record the partial pressures of the reactants and the reaction products. This combination of techniques enables us to directly correlate the measured reaction rates and reaction kinetics with the catalyst structure and composition. Examples will be shown for the oxidation of carbon monoxide on several metal surfaces. We find that under reaction conditions, surface oxides are formed that we identify as the most active phase. We observe spontaneous, self-sustained reaction oscillations that will be explained in terms of periodic metal-oxide transitions.